Bah... I had a nice long post with hyperlinks and pictures of my new computer parts due to 40 clicks and I clicked the close tab button and lost it all.
You use Firefox, right? Don't you know? You can get tabs back, and usually with all the stuff you typed still existing if you do one of two things:
1) Right click in the tab area and select "Undo Close Tab"
2) Under the History menu, go to the hierarchal menu of "Recently Closed Tabs" and find the one you accidentally closed.
The first option only works if you still have more than one tab open. The second option is always available. Both should have the same results with no information lost. (Provided you didn't close the whole browser window.)